1. Field of the Invention
The invention is directed to a process for printing onto the surface of a poly(vinyl chloride) resin substrate, virgin or dye colored, which printed matter does not change its configuration on standing, as in storage. Also the invention is directed to overprinting dye colored poly(vinyl chloride) resin, where said overprinted matter retains it own distinct color.
2. Description of the Prior Art
Poly(vinyl chloride) resins are colored in several ways. A dye, or mixture of dyes, soluble in the resin is introduced into resin which is in a more or less molten condition to obtain a dye/resin solution. A dye may be dissolved in a plasticizer and the solution incorporated into the particular resin; in this instance, the dye need not soluble in the resin itself. Or the dye may be added to the molten plasticized resin to obtain the dyed plasticized resin. Or the plasticizer soluble dye may be painted on the plasticized resin surface; on standing the dye migrates into the plasticizer and gives the body color. These are some different procedures for mass dyeing of the plastic body.
More commonly an ink formed from a soluble dye and a solvent therefore, which solvent has some solubility for the resin, giving some penetration into the resin substrate is used to color the surface of the resin body. Dye/halogenated solvent inks, as disclosed in copending application Ser. No. 424,058, filed 09/27/82, by Ulry/Cosner/Ryan, are preferred soluble dye/solvent inks. These have the great advantage of being nonflammable.
The soluble dye/solvent inks have drawbacks. They cannot be used to overprint, as printing or as a colored area, resin which has been mass dyed with soluble dye; the overprint dye adds to the underlying dye color and the overprint color changes to an undesired color. Also the soluble dye/solvent inks cannot be used to overprint lettering or other impressions onto resin which has been mass dyed with soluble dye, or onto virgin resin, because the dye migrates sidewise, blurring the edges of the printed matter and eventually rendering the letter illegible and the impressions become a colored blob.